Patent GB-409904-A (GB)
Title: Improvements in or relating to alternating current interruptors
IPC: H01H33/44
Filed: 1933-05-12
Abstract: 409,904. Arc rupturing in switches. SIEMENS - SCHUCKERTWERKE AKT.- GES., Siemensstadt, Berlin. May 12, 1933, No. 13915. Convention date, May 14, 1932. [Class 38 (v).] An A.C. circuit-breaker for power current circuits is provided with means whereby its contacts, in opening, in addition to a continuous contact-opening movement, are set in oscillation relatively to one another in synchronism with the current flowing through the switch and of double or approximately double the A.C. frequency. The oscillations reduce the contact separation at current maximum and increase it at current zero, thereby facilitating extinction of the arc at the latter. In Fig. 1 a main movable contact 27 encloses a pin 29 which is mounted on an insulating piston 28 and is slidable within an insulating sleeve 31. On separation of 27 from the fixed contact 25, the arc jumps to pin 29 and the current traverses a spring 30 connected between 27, 29. If the current is at a maximum, spring 30 contracts and lowers contact 29 to keep the arc short, but as the current drops to zero and 30 expands, the upward movement of 29 is superimposed on that of 27 so that the gap at current zero is a maximum. In Fig. 2, a spring 59 in series with the contacts 57, 50 is unlocked by means not shown and, when the amplitude of oscillation is sufficient, a member 63 breaks a toggle and releases a latch 56 from a sleeve 52, which is then drawn down by a spring 54 and moves contact 50 to position 64, which corresponds to the then position 65 of contact 57. When the current diminishes and drops to zero, spring 59 expands, so that at current zero the separation of the contacts is a maximum. The springs are of an alloy of aluminium or magnesium capable of being tempered and may be energized from the line being interrupted by readilysaturable current transformers. The Specification as open to inspection under Sect. 91 described (with drawings) also the following. Each turn of a helix insulatingly carried a contact, the contacts being all in engagement with one another in the closed position. The helix was energized by a current transformer in the line containing the contacts and normally locked in the contracted position, the lock being released to allow opening. The chamber for such parts might contain oil, water, or resistance liquid, or the switch might be operable in a vacuum, or on the expansion or deionization or air-blast principle. The contacts might also be large enough to keep the current-density below arcing value. In another form, a helix is energized by a shunt circuit (normally short-circuited) from the line and is in series with a pair of contacts in shunt to main contacts. When the amplitude of oscillation of the helix is large enough, the main contacts are tripped open by the movable shunt contact, which is actuated by the helix. The shunt contacts are then in engagement at current maximum, and as the current falls, the movable shunt contact separates from its fixed co-operating contact. At current zero the separation is a maximum. A half-wave eliminator for rectification purposes is also illustrated and comprises a pair of parallelarranged leaf springs which insulatingly carry at their ends contacts in the main circuit. A potential transformer energized from the latter sends a current through a rectifier down one spring and up the other, so causing the springs to diverge electrodynarnically and bring the contacts together. This subject-matter does not appear in the Specification as accepted.